1. Field of the Invention
The present invention relates to the technical field of NMR spectrometers for examining the structures of substances using nuclear magnetic resonance phenomena and, more particularly, to the technical field of devices for supplying local signals used to generate plural resonance frequency signals.
2. Description of Related Art
A conventional NMR spectrometer is essentially constructed as shown in FIG. 4. This instrument has a magnet 1 within which a sample 2 is placed. An RF pulsed signal of a resonance frequency corresponding to the magnetic field strength is applied to the sample 2 to induce a nuclear magnetic resonance phenomenon. In this case, the resonance frequency signal is generated by mixing a local signal and an intermediate frequency signal within a resonance frequency signal generator 5. The local and intermediate frequency signals are generated by a local signal generator 3 and an intermediate frequency signal generator 4, respectively. The resonance frequency signal is appropriately amplified by an amplifier 6 and fed via an input/output switching device 7 to a detector 8 consisting of a detection coil. The resonance frequency signal is applied as an RF signal to the sample 2 from the detector 8. The sample 2 produces a signal of the resonance frequency because of a nuclear magnetic resonance phenomenon. The produced signal is picked up by the detector 8. The output signal from the detector 8 is sent to a preamplifier 9 via the input/output switching device 7 and amplified. Then, the signal is converted into audio frequency by a receiver 10 and converted into digital form by an A/D converter 11. The resultant digital signal is accepted into a computer 12 which analyzes the signal. Thus, the sample 2 is analyzed. In this manner, the structure of the substance is examined by the NMR spectrometer.
It is customary to apply plural RF signals that are different in frequency, amplitude, or phase to a sample simultaneously or in succession, in order to examine the structure of the substance more closely. Accordingly, another conventional NMR spectrometer uses plural (five in the illustrated example) resonance frequency signal generators 5 to generate plural resonance frequency signals as shown in FIG. 5. To obtain plural resonance signals, there must be the same number of local signal generators 3 (five in the illustrated example) and the same number of intermediate frequency signal generators 4 as there are the resonance frequency signal generators 5.
Normally, the amplifier 6, the input/output switching device 7, the detector 8, and the preamplifier 9 have their respective fixed operating frequency ranges. Therefore, they need to be used separately according to frequency. Consequently, a router 13 is placed ahead of the amplifier 6 to use these components separately according to different frequencies.
The conventional local signal-supplying device designed in this way and used with an NMR spectrometer needs the same number of local signal generators 3 as there are the resonance frequency signal generators 5. Therefore, the number of the local signal generators 3 is increased, thus increasing the cost.
It is an object of the present invention to provide a local signal-supplying device which is for use with an NMR spectrometer and can be fabricated at reduced cost by reducing the number of local signal generators.
This object is achieved in accordance with the teachings of the present invention by a local signal-supplying device which is used with an NMR spectrometer and which comprises: local signal generators for generating local signals; and resonance frequency signal generators for generating resonance frequency signals using the local signals. RF signals obtained based on the resonance frequency signals from the resonance frequency signal generators are applied to a sample to induce nuclear magnetic resonance phenomena in the sample. The local signal-supplying device is characterized in that the resonance frequency signal generators are plural in number and that there are further provided local signal-distribution devices for dividing the local signals generated by the local signal generators into the same number of portions as there are the resonance frequency signal generators and supplying the local signals to the resonance frequency signal generators, respectively.
In one feature of the present invention, the aforementioned local signal generators generate local signals that are spaced in frequency.
In another feature of the present invention, the aforementioned local signal generators are fewer in number than the resonance frequency signal generators.
In a further feature of the present invention, the local signal-distribution devices are at least equal in number to the corresponding local signal generators.
In a still other feature of the present invention, there are provided local signal-switching devices as devices for selecting a certain one of the plural local signals distributed by the local signal-distribution device and supplying the selected signal to the resonance frequency signal generators.
In yet another feature of the present invention, the local signal-switching devices are at least equal in number to the corresponding resonance frequency signal generators.
In an additional feature of the present invention, the local signal-distribution devices and the local signal-switching devices together form one local signal-distributing-and-switching device.
In still another feature of the present invention, the local signal-distribution device and the local signal-switching device are incorporated in the resonance frequency signal generators.
In a still further feature of the present invention, the local signal-distribution devices incorporated in the plural resonance frequency signal generators are connected in cascade such that at least one output of the local signal-distribution device of one resonance frequency signal generator forms inputs to the local signal-distribution device incorporated in the next one of the resonance frequency signal generators.
In a yet further feature of the present invention, in the last one of the cascaded resonance frequency signal generators, output from the immediately previous local signal-distribution device is directly applied to a corresponding terminal of the incorporated local signal-switching device.
Other objects and features of the invention will appear in the course of the description thereof, which follows.